Clinostomids are a group of digeneans in which substantial diversity has been recently discovered, with some metacercariae specific to their fish hosts. Genetic analysis has been instrumental in elucidating species diversity within this genus. Recently, seven COI lineages were reported in Argentina, along with three metacercarial morphotypes lacking molecular data. Two of these were found parasitising Rivulidae fishes. The discovery of Clinostomum metacercariae in Trigonectes aplocheiloides and Titanolebias monstrosus from temporary ponds in the western Chacoan region allowed us to redescribe the metacercariae previously identified by other authors and provide the first sequences of this lineage. The morphology of the metacercariae in both hosts matched previously reported descriptions. Genetic analysis clustered the new lineage with Clinostomum detruncatum, Clinostomum sp. 7, Clinostomum L1, and Clinostomum CRA. This discovery leaves only two morphological records of metacercariae to be characterised using DNA sequencing: one in another Rivulidae (Neofundulus paraguayensis) and one in a Loricaridae (Hypostomus sp.). The present results represent the eighth clinostomid lineage sequenced from Argentina, highlighting the extensive diversity in South America and the many lineages yet to be described or identified, considering that only one of these lineages is formally described based on adult specimens found in the heron Ardea cocoi.

In this study, we use an integrative taxonomic approach to redescribe Schyzocotyle nayarensis (Malhotra, 1983) (Cestoda: Bothriocephalidae), based on newly collected specimens from the type-host Raiamas bola (Hamilton, 1822) (Cypriniformes: Danionidae) in Fulbari, Siliguri, West Bengal, India. The detailed morphological assessment, from whole mounts, histology and scanning electron microscopy, offers additional insights into the scolex structure, vitelline follicles, and egg morphology. Molecular data from this and previous studies corroborate the identity and systematics of S. nayarensis as a bothriocephalid closely related to the Asian Fish Tapeworm, Schyzocotyle acheilognathi (Yamaguti, 1934). This study elucidates the historical context and taxonomic ambiguities surrounding S. nayarensis, emphasizing the key role of the scolex in both generic and species identification. Amendments to the diagnosis of Schyzocotyle Akhmerov, 1960 are proposed. A differential diagnosis of the two valid species within the genus, namely S. acheilognathi and S. nayarensis, is also provided. An evaluation of the taxonomic status of Bothriocephalus teleostei Malhotra, 1984, and Capooria barilii Malhotra, 1985 suggests that they may be S. nayarensis. Finally, we posit that none of the ten species of Ptychobothrium Lönnberg, 1889 described from Indian freshwater teleosts belong to this genus but instead appear to be a mix of species belonging to Schyzocotyle, Senga Dollfus, 1934, and possibly even Proteocephalidae La Rue, 1911; all require further study based on newly collected, properly fixed specimens and an integrated taxonomic approach. Finally, future survey studies may reveal hidden diversity of Schyzocotyle species in Indian cyprinoids.

Mylonchulus laocaiensis sp. n. recorded from Vietnam, is described and illustrated, and its phylogenetic relationship within the Mylonchulidae family and Mononchida order are analysed. The new species is characterized by medium body size (L = 1.0–1.5 mm); buccal cavity goblet shaped, 26–29 × 14–16.5 μm or 1.8 (1.7–1.9) times as long as wide; posterior position of dorsal tooth apex (79%–88% from the base of buccal cavity); a small subventral tooth present on subventral wall; pars refringens vaginae with faint and small (2.5 × 1.7 μm) teardrop-shaped pieces, short pars distalis vaginae; male with short spicules (54–57 μm) with rounded head. The molecular data (18S and 28S rDNA) are provided for the new species.

In this study, we describe a new species of Pseudoparacreptotrema (Allocreadiidae) from the mugilid Dajaus monticola collected in western Puerto Rico, where no allocreadiid has previously been reported, bringing the number of species in this genus to seven (five in D. monticola, two in Profundulus spp.). The new parasite species is distinguished from congeners by its overall size, oral-to-ventral sucker size ratio, pharynx size, cirrus sac, and oral lobe morphology, and by 0.64%–3.45% divergence in a 1019-bp alignment of 28S. We build on prior suggestions that the current concept of P. agonostomi likely includes multiple species and provide the first mitochondrial data (whole mitochondrial genome) as well as the complete nuclear rDNA array from Pseudoparacreptotrema to facilitate future phylogenetic work. Within the Allocreadiidae, phylogenetic analysis of mitochondrial genomes and 28S provides conflicting topologies for the placement of Pseudoparacreptotrema and Allocreadium. The 28S phylogeny of six species of Pseudoparacreptotrema resembles that of four lineages of D. monticola in that in both host and parasite, Pacific coastal lineages branch earliest, and a Caribbean lineage is more recently evolved.

We described Creptotrema cambeve n. sp. from the intestine of the Brazilian catfish Cambeva davisi (Haseman, 1911) (= Trichomycterus davisi) based on integrative analyses using morphological and molecular approaches. Creptotrema cambeve n. sp. closely resembles morphologically Creptotrema paraense Vicente, Santos & Souza, 1978, which was described from a siluriform fish in Northern Brazil; however, the two species differ mainly in the oral and ventral sucker sizes and the distribution of the vitellaria. The phylogenetic analyses of the 28S rDNA placed the sequences of the new species in a monophyletic clade together with all other Creptotrema spp. and as sister taxon of Creptotrema cruste Alcantara, Ebert, Ferreira-Silva, Forti, Morais, Pérez-Ponce de León & Silva, 2024, a parasite from a Brazilian anuran. Genetic divergences between the new species and other Creptotrema spp. varied from 0.2% to 4.3%, further corroborating the distinction of the new taxon. Creptotrema cambeve n. sp. is the 18th nominal Creptotrema species known from South America and the 22nd erected in the genus. This is the first study reporting a trematode in Cambeva spp. hosts and the second parasitological survey carried out for Ca. davisi, a poorly known small endemic fish.

Three new species of Gyrodactylus were identified from the body surface of the Triplophysa species from the Qinghai-Tibet Plateau, Gyrodactylus triplorienchili n. sp. on Triplophysa orientalis in northern Tibet, G. yellochili n. sp. on T. sellaefer and T. scleroptera and G. triplsellachili n. sp. on T. sellaefer and T. robusta in Lanzhou Reach of the Yellow River. The three newly identified species share the nemachili group species’ characteristic of having inturning hamulus roots. Gyrodactylus triplorienchili n. sp. shared a quadrate sickle heel and a thin marginal hook sickle, two morphological traits that set them apart from G. yellochili n. sp. However, they may be identified by the distinct shapes of the sickle base and marginal hook sickle point. Gyrodactylus triplsellachili n. sp. had much larger opisthaptoral hard part size than the other two species. The three new species show relatively low interspecific differences of 2.9–5.3% p-distance for ITS1-5.85-ITS2 rDNA sequences. Phylogenetic analysis indicated that the three new species formed a well-supported monophyletic group (bp = 99) with the other nemachili group species.

The cyst nematodes, subfamily Heteroderinae, are plant pathogens of worldwide economic significance. A new cyst nematode of the genus Cactodera within the Heteroderinae, Cactodera xinanensis n. sp., was isolated from rhizospheres of crops in the Guizhou and Sichuan provinces of southwest China. The new species was characterized by having the cyst with a length/width = 1.3 ± 0.1 (1.1–1.6), a fenestral diameter of 28.1 ± 4.3 (21.3–38.7) μm, vulval denticles present; second-stage juvenile with stylet 21.5 ± 0.5 (20.3–22.6) μm long, tail 59.4 ± 2.0 (55.9–63.8) μm long and hyaline region 28.7 ± 2.7 (25.0–36.3) μm long, lateral field with four incisures; the eggshell with punctations. The new species can be differentiated from other species of Cactodera by a longer tail and hyaline region of second-stage juveniles. Phylogenetic relationships within populations and species of Cactodera are given based on the analysis of the internal transcribed spacer (ITS-rRNA), the large subunit of the nuclear ribosomal RNA (28S-rRNA) D2-D3 region and the partial cytochrome oxidase subunit I (COI) gene sequences here. The ITS-rRNA, 28S-rRNA and COI gene sequences clearly differentiated Cactodera xinanensis n. sp. from other species of Cactodera. A key and a morphological identification characteristic table for the species of Cactodera are included in the study.

A new species of bothriocephalid cestode in the genus Anantrum is described from the intestine of the shorthead lizardfish Synodus scituliceps from the north Pacific coast of Costa Rica. The new species is described based on an integrative taxonomic approach that includes the use of light and scanning electron microscopy, 28S rDNA sequencing, and phylogenetic analysis. Anantrum gallopintoi sp. nov. is the third known member of this genus and can be distinguished from A. tortum (Linton, 1905) and A. histocephalum Jensen & Heckmann, 1977 by a combination of morphological and ecological traits and, in particular, by having a vaginal sphincter, different number of testes, and different type host and type locality. The molecular analysis and the phylogenetic reconstructions supported its status as a new taxon placing it within a well-supported separate branch of Anantrum spp. subclade. According to the present finding, S. scituliceps represents a new host record and Costa Rica a new geographical record for Anantrum species, and, in general, for a bothriocephalid cestode.

Despite a great effort made for almost 90 years, the diversity of freshwater fish trematodes in Mexico is still far from being fully known. The addition of molecular data to the description of trematode diversity in the last two decades added the potential to establish more robust species limits and a more accurate biodiversity estimation, but also led in some instances to the recognition of cryptic species complexes. Here, we used sequences of the large subunit of the nuclear ribosomal gene (28S rRNA) as barcodes, and morphological data, to assess the diversity of freshwater fish trematodes from a lake within a tropical rainforest. Eighty freshwater fish specimens of eight species were studied, and 120 trematode specimens were collected. Morphologically, specimens were allocated into nine genera; molecular phylogenetic analyses along with sequence divergence data provided evidence for recognising 11 trematode taxa, six adults and five metacercariae; six of them were identified to species level. Geographical distribution and host association patterns are briefly discussed for each trematode taxa.

Gender equity and authorship diversity are believed to be the essential parts of building a dynamic scientific atmosphere. The purpose of the present study was to determine the status of gender equity in research on echinococcosis and the editorial diversity in major parasitology journals over the past four decades. All articles were retrieved from major databases from the years 1980, 2000, 2010, 2015, and 2020. Journals belonging to the four quartiles of parasitology journals listed in the Journal Citation Report were selected, and the gender and region of each editorial member were identified. Among the 3583 first authors of the articles published in all selected years, 2236 (62.4%) were men, whereas 1040 (29%) were women. There was a significant increase in women’s contributions as the first author, from 6.8% in 1980 to 35.8% in 2020 (P < .001). A greater gender gap was found for the senior authors, showing 2391 (66.7%) men and 837 (23.4%) women. The gender gap has been narrowed in most of the six regions of the world, particularly for the Western Pacific region, where the gender inequity had almost diminished in 2020; i.e. the man-woman ratios of the first and last authors from this region were 2.25 and 1.75 in 1980, reaching 1.04 and 0.97, in 2020, respectively. Our findings also indicated that articles authored by men received 2.5 to 3.1 times more citations than women authors. Gender distribution of the editors-in-chief, associate editors, and editorial board members across all quartiles showed that 78.7%, 69.5%, and 72.7% were men, respectively, and mostly affiliated with the European and American regions. Findings of the present study showed that gender inequity is still present and women researchers continue to be the minority in the field of parasitology, particularly in the research on echinococcosis.

Phylogenetic studies of aberrant species are of considerable scientific interest because their taxonomic rank in traditional systems based on morphological characters is not infrequently overestimated. Apopharynx bolodes (Braun, 1902) is one of the few psilostomid digeneans devoid of the pharynx. This is considered a sufficient basis for assigning it and similar species to the subfamily Apopharynginae. We found A. bolodes in Fulica atra Linnaeus, 1758 from Belarus, described it morphologically, and genotyped it by the 28S rRNA gene and the ITS2 region. It is the first molecular data on A. bolodes and the first record of this digenean species in Belarus. The phylogenetic analysis based on partial sequences of the 28S rRNA gene showed that A. bolodes is closely related to the Sphaeridiotrema spp. (Sphaeridiotrematinae). However, this phylogenetic inference has not received yet support with data on the ITS2 region.

The entomopathogenic nematode (EPN), Steinernema yirgalemense, is an effective biological control agent against a variety of important insect pests in South Africa. To develop a South African EPN product feasibly in South Africa, EPNs need to be mass-produced. This study aimed to record the population dynamics of S. yirgalemense with in vitro liquid production in shake flasks, with a protein source of powdered egg yolk. The Erlenmeyer flask results indicated variation between flasks, albeit still achieving high yields. The reasons for attaining such variability in the recovery, yield, and growth stages are unclear, hence requiring further studies seeking to increase consistency. The results obtained indicate that, when IJ recovery is low, yields are also low due to relatively few reproductive adults being present in solution, which, in turn, produces more offspring, which later converts to the desired infective juvenile used for product formulation development. For commercial viability, a consistent production system is required that produces predictable yields. This study showed comparable high yields achieved with the flasks and in an early-stage bioreactor setup, being a positive development for S. yirgalemense mass production. Prior to the bioreactor scale-up process, protocol of mass production, the population and growth dynamics of the nematodes in the flask environment requires understanding. This is a positive step, leading to the future commercialisation of a local EPN product.

Aplectana hylambatis (Baylis, 1927) is a widespread nematode in South America that infects different species of anurans from different families. Although the morphology of this species shows intraspecific variations and is well studied, A. hylambatis does not have genetic characterisation. Therefore, the present study aimed to provide the first genetic characterisation of this parasite, based on 18S and 28S rDNA sequences, as well as to evaluate its phylogenetic position in the family Cosmocercidae. The present specimens showed no major morphological variations and were assigned to A. hylambatis mainly based on the shape of spicules and the presence of mamelon-like structures slightly anterior to the vulva. The genetic characterisation confirmed the close relationship between A. hylambatis and other cosmocercids, and the 28S sequences were more informative for phylogenetic reconstruction, especially for those relationships at higher and intermediate levels. Aplectana hylmabatis was in a basal position within a clade formed by other congeners and species of Cosmocerca. The geographic origin may have influence in the divergence process of Aplectana spp. and genus was non-monophyletic and closely related to Cosmocerca, similar to previous findings. The present results will be useful for future studies on the phylogeny of Cosmocercidae, since several genera and species in this family still lack genetic characterisation. Furthermore, the 28S sequences can be useful in genetic studies of A. hylambatis populations, since this species appears to have phenotypic variations.

The present study aims to describe a new genus and species of microphalloid digenean parasite of two species of bats of the genus Peropteryx from the Mexican Neotropics (in the states of Chiapas and Yucatán). Morphological and molecular data (28s rDNA ribosomal gene sequences) were used to study Digeneans. Sagittatrema zutzi gen. nov. sp., nov., is diagnosed morphologically by having a sagittiform body, a genital pore in the midline of the body, posterior to the ventral sucker, and a cirrus sac running through much of the diameter of the ventral sucker. The nine sequences generated from the 28S rDNA gene were used to examine the phylogenetic affinities of this new taxon within the superfamily Microphalloidea Ward, 1901, using Maximum Likelihood and Bayesian Inference analyses. Both analyses resulted in trees with similar topologies and formed a well-supported clade (Bt = 100; pp = 1) with the Sagittatrema sequences. Because of the new genus’s phylogenetic position and that some sister families to the proposed taxa, like Pleurogenidae and Prosthogonimidae, are polyphyletic, we prefer to consider Sagittatrema as a genus incertae sedis within Microphalloidea. A full systematic review of microphalloids is needed to confirm their phylogenetic position.

Ascaridoidea (Nematoda) is a widespread superfamily of nematodes that comprises gastrointestinal parasites from all major groups of vertebrates. Although this taxon probably emerged in the Carboniferous, its Brazilian fossil record includes mostly eggs, found in ancient remains, collected in paleontological and archeological sites from the Mesozoic and Cenozoic Eras. The Tremembé Formation (Oligocene of the Taubaté Basin) has become an important source for paleoparasitological studies in avian coprolites during the third decade of the 21st century, with reports of eggs only at only a single cell stage, of embryonic development. Here we present the first egg of Ascaridoidea preserved containing morula, from a bird coprolite recovered from the shales of the Tremembé Formation. Three coprolites, from the outcrop of Aligra Comércio de Argila S/A, Taubaté municipality (State of São Paulo), were rehydrated and subjected to spontaneous sedimentation. Based on morphological and morphometric features and diet and zoopaleontological context, the trace fossils were assigned to piscivorous birds. The egg found showed morphological characteristics typical of Ascaridoidea: namely spherical form, ornamented, and somewhat thick shell. Moreover, this superfamily includes several taxa that infect piscivorous birds and fish in heteroxenous life cycles and produce eggs with similar features as the egg found in the present study. The paleoparasitological information associated with the paleofaunistic diversity of birds and fish from the Tremembé Formation, reveal that the ancient Brazilian paleoenvironments provided subsidies for the rise and success of nematodes infecting these animals during the Paleogene.

The relationship between Schistosoma mansoni (Sm) and hepatocellular carcinoma (HCC) has been evaluated by many studies that point towards a co-relation between schistosomal infection and HCC. While many such studies demonstrated that Sm infection in the presence of another carcinogenic factors leads to HCC, none of these studies could conclusively prove the cancer-inducing ability of Sm in humans, independent of other carcinogenic factors. The aim of this work is to present the current understanding on the association of Sm with HCC. Many epidemiological, pathological, and clinical studies have shown the role of multiple events like chronic inflammation and fibrosis as well as hepato-toxic agents like soluble egg antigens (SEAs), which help in creating a micro-environment which is suitable for HCC development. The role of Sm infection and deposited eggs in causing persistent inflammation, advanced fibrosis, and the role of SEAs, especially IPSE/alpha-1, is emphasised. This work concludes that Sm infection has the potential to induce cancer independently but the same has not been reported in humans to date. Extensive research is required to establish a causal relationship between Sm infection and HCC induction, or a complete lack thereof. However, Sm infection definitely acts along with other carcinogenic factors to induce HCC at a much faster pace and also leads to an aggressive form of liver cancer, which the other carcinogenic factor could not have achieved alone.

Active components from plants are an alternative therapy to parasite control, addressing the widespread multidrug resistance populations. Linalyl acetate (LA), an ester abundantly found in plants of the genus Lavandula, was tested in vitro against third-stage larvae (L3) of Haemonchus spp. and Trichostrongylus spp. using the larval migration test at 0.89, 2.24, 4.47, 8.95, 17.9, 35.8, 71.6, and 143.2 mg/ml. After an initial incubation of 18 h, the total content of each tube was transferred to a 24-well plate that allowed active L3 to migrate through a nylon mesh (second incubation). Although LA exhibited 100% efficacy in reducing larval migration at 8.95 and 17.9 mg/ml, it showed reduced activity (5%) at 143.2 mg/ml. The data revealed a hormetic biphasic response characterised by an inverted U-shaped concentration-response curve. While hormesis has been previously documented in insecticidal and allelopathic contexts, this study reports the occurrence of hormesis induced by a phytochemical component against two species of nematodes for the first time. This distinctive stimulation-and-inhibition effect should be considered when selecting new compounds for preclinical testing.

We describe a new species of the genus Alippistrongylus (Nematoda: Trichostrongylina) in the small intestine of Delomys dorsalis (Rodentia: Sigmodontinae) found in Itatiaia National Park (Parque Nacional do Itatiaia, PNI), state of Rio de Janeiro, Brazil. The new species can be distinguished between the other two species previously described by the following morphological characteristics: pattern of the rays from the caudal bursa rays in males and the spherical-shaped appendage in the female. Additionally, we provide molecular genetic data from the new species. The discovery of Alippistrongylus itatiaiaensis sp. n. expands our understanding of nematode diversity and underscores the importance of parasite studies in biodiversity conservation. Its occurrence in a preserved area like the PNI emphasises the role of such habitats in maintaining unique ecological interactions.

Members of the genus Maritrema Nicoll, 1907 include endoparasites of aquatic birds and mammals, distributed worldwide. Adult specimens were collected from the intestines of three bird species (the great black hawks, Buteogallus urubitinga Gmelin; laughing gull, Leucophaeus atricilla Linnaeus; and the willet, Tringa semipalmata Gmelin) in three localities along the Gulf of Mexico. Photogenophores were sequenced for the large subunit (LSU) from nuclear rDNA, and the new sequences were aligned with other microphalloid sequences available in GenBank. The maximum likelihood and Bayesian inference analyses revealed three independent lineages, one corresponding to a previously described species, Maritrema corai Hernández-Orts, Pinacho-Pinacho, García-Varela & Kostadinova, 2016, and two representing two undescribed species. These two new species are described in the current study. Maritrema itzamnai n. sp. can be morphologically differentiated from its four congeneric species occurring in coastal areas of Mexico by having smaller oral (20–29 × 20–38 μm) and ventral (20–39 × 19–33 μm) suckers. In addition, Maritrema itzamnai n. sp. possess annular vitellarium instead of a horseshoe-shaped vitellarium. Maritrema kukulkanni n. sp. can be distinguished from its congeneric species reported from Mexico by possessing a larger oesophagus (44–117μm) and by having a vitellarium distributed in both the hindbody and forebody. Maritrema corai is the third species recorded in this study parasitizing the great black hawk (Buteogallus urubitinga); this represents a new host and locality record, expanding its distribution range from the Mexican Pacific Ocean to the Gulf of Mexico.

Species-level delineation of digenetic trematodes is complex and can be best achieved by integrative taxonomy using both genetic characterisation and morphological analysis. Two new Bucephalidae species of the genus Rhipidocotyle Diesing, 1858 are described here based on specimens collected from the intestine of Sphyraena putnamae Jordan & Seale following this approach. Adults of R. siphonyaka n. sp. and R. nolwe n. sp. possess tentacles and a tegument with scales. They are distinguished from their congeners by the arrangement of the digestive structures, the extent of the uterus relative to vitelline fields, and the arrangement of the reproductive structures. Rhipidocotyle siphonyaka n. sp. differs from R. nolwe n. sp. in having the pharynx and mouth positioned in the pre-uterine field, tandem testes, longer body length, and shorter pre-vitelline and post-testicular distance. Rhipidocotyle siphonyaka n. sp. differs from its congeners in having a tube-like intestinal caecum, pharynx and mouth opening positioned in the pre-vitelline field. Rhipidocotyle nolwe n. sp. appears to be similar, morphologically and morphometrically, to Rhipidocotyle khalili (Nagaty, 1937). Despite their similarities, R. nolwe n. sp. has a shorter body length and egg size. Moreover, the molecular analysis of 28S and ITS rDNA fragments indicate that R. siphonyaka n. sp. and R. nolwe n. sp. are closely related phylogenetically but distinct from one another and other Bucephalidae for which molecular data are available.